This invention relates to power cable. More particularly, it relates to power cable having a reduced magnetic field.
It is known that electrical power cable generates a magnetic field around the cable. The more current that passes through the AC power cable, the larger the magnetic field surrounding the cable. Extension cords or power cords from electrical or electronic components also have a magnetic field surrounding the cable. This magnetic field has been known to contaminate or damage magnetic components, such as audio/videotapes, computer hard drives, floppy disks, etc. Also, it is believed that this magnetic field represents a health hazard to humans if they are in close proximity to the cable and thus are exposed to the magnetic field. One way to reduce the likelihood of this damage or health hazard is to isolate the power cable from components or humans. One way to isolate the power cable is simply to maintain the cable at a substantial distance from components or humans, such as in the case of power transmission lines where the cable is placed on tall towers. Another way to isolate the power cable is to provide shielding about the cable. Shielding techniques are taught in U.S. Pat. Nos. 5,349,133 issued to Rogers and 5,530,203 issued to Adams et al. However, in common household applications, such as the use of extension cords, electrical or AC power cords, or drop wire, isolation of the cable by distance is not practical and isolation of the cable by use of shields adds substantial costs to the cable.
It is, therefore, one object of this invention to provide an improved power cable.
It is another object of this invention to provide a power cable having a reduced magnetic field about the cable when current flows through the cable.
It is further another object of this invention to provide a natural surge and AC spike suspension down the AC cable.
It is still another object of this invention to provide a reduced magnetic field power cable which is inexpensive to manufacture.
In accordance with one form of this invention there is provided an electrical power cable, including an elongated carrier. First and second power conductors are provided. Each of the first and second power conductors are electrically insulated. One end of each of the power conductors is adapted to be connected to a source of electrical energy. The other end of each of the power conductors is adapted to be connected to a load. The first power conductor is spiraled about the carrier in one direction. The second power conductor is spiraled about the carrier in the opposite direction to the first power conductor, whereby the magnetic field about the cable caused by current flowing through the power conductors is reduced. Preferably, the carrier is a flexible hollow conduit, round flexible material or cable. Also, preferably, the first conductor is at approximately a 45xc2x0 angle with respect to the longitudinal axis of the carrier and the second conductor is also at approximately a 45xc2x0 angle with respect to the longitudinal axis of the carrier so that the first and second conductors cross one another at approximately a 90xc2x0 angle.
In accordance with another form of this invention, there is provided a method for reducing the magnetic field about an energized power cable by provided an elongated carrier, and first and second insulated power conductors. The first power conductor is spiraled about the carrier in one direction, while the second power conductor is spiraled about the carrier in the opposite direction to the first power conductor. One end of the power conductors are connected to a source of electrical energy and the other end of the power conductors are connected to a load. The magnetic field produced by the current flowing through the first and second power conductors is reduced because the power conductors are spiraled in opposite directions and the magnetic field is cancelled out.
Since the magnetic field associated with power conductors is substantially eliminated, communication cable, including unshielded communication cable, may be placed in close proximity to the power conductors. The teachings of the subject invention may be used to construct a combination power and communication cable by placing a communication cable within the carrier. In the case where the carrier is a hollow conduit, the communication cable may be placed within the conduit.